Well casing perforator



Feb. 23, 1960l D. s. MKEE WELL cAsING PERFoRAToR Filed Dec. 13, 1955INVENTOR,

n w f/ /7 L. Tl////////////////// n :|11 7/ /7/ |.i .l MW N am w E /MIIL 1L w WELL CASING Bannon/tron DonovanaS'. McKee, GirlahomaCity,"0kla., assignor, by

mes'n'e assignments; to"`Borg-lvarne'rA Goitporation, Vernon, Calif.,acorporationI of Illinois `This invention relates to improvements inmeans for performing perforating operations in oil and` gas wells,andmore specifically to improvements inso-called perforating guns. 'v AIn the processof completing an oil or gas well `after the borehole hasbeen drilled and casing run in and cemented, perforationsaretformedthrough the casing and cementfat ther level of the productive strata, topermit inflow of fluid into the well. The perforations are commonlyproduced by bullets, or by shapedl explosive charges, `which are firedfrom a gun orV perforator suspended in the well. The present inventionrelates particularlyto perforating apparatus using the shapedcharge typeofperforating unit, andspecifically to improvements in the meansemployedy to initiate explosion or detonation of the shaped-charges.

It is customary practice to detonate or initiate a plurality or stringof shaped-charges in rapid succession by detonating la length ofPrimacord or similar detonable fuse which extends through oradjacent-,to each ofv the. shaped-charges. The Primacordor otherdetonable means is structurally similar to an elongate cord, and forreasons of safety andconvenience, among others, is `formed withf anexplosive which is not detonable by ordinary heat orvmechanical or otherhandling shock. Accordingly, a special means, *such as a blasting cap,has customarily been employedv to initiate detonation of the Primacord.As is Well' known, blastingcaps a-nd simi-lar detonating means aresensitive to heat, shock, and other environmental conditions, whichrenders their employment hazardous to personnel and equipment in theirvicinity and necessitates special caution in handling. Since well casingperforat-ing guns must oftenbe serviced or reloaded in the held; thehazard presentedl by the use of blasting caps or similar sensitivedetonators is accentuated by the unfavorable environmental conditionsthere encountered, Vand by the fact that loading might have to beperformedby relatively unskilled personnel.

Efforts have been made to overcome the dangers inherent in or' presentedby the use of the aforementioned sensitive detonators; and one markedlysuccessful and relatively safe detonator means for 'detonating aPrimacordo'r other safe type of shaped-charge detonator has beenintroduced into commercial well casing perforating operations, thedetonator means comprising onlyV substances and materials quiteinsensitive; to thermal and mechanical shock and abrasioni.` Thatdetonator means, as 'employed in a typical shaped-charge perforatinggun, is disclosed in a co-pending applicationof Houck and Bradshaw,Serial No'. 399,032, led December 18, 1953, now US. Patent No.2,883,931, issued April 28, 1959. The present inventionr constitutes animprovement upon the detonator means disclosed in that application'.

They detonator means disclosed in the aforementioned applicationcomprises means to position and hold af portion of a length of Primacordor other shock-insensitive .detonable fuse in' the pathA of a projectilein the form arent 2,925,775 Patented Feb.` 23, 1960 of; a fragment or'pellet propelled at high (detonating) speed by` other relatively safeshock insensitive means. The latter means includes a chamber means inwhich a deagrable charge is adapted to burn under the initiatingactionjof an electric fuse or wire. The combustible charge is confined'in the chamber until sufficient pressure is produced tol shear a pelletor particle out of a disc seated in one end ofthe chamber; and thepellet, when sliearedI from the disc, is propelled with great speed intodetonatingf contact or impingement with the Primacord` (or with abooster charge attached to the Primacord), preferably being guidedmeanwhile by suitable pellet path defining or restricting means.

While the aforedescribed previously disclosed structure presents nohazard from the eld loading standpoint in so far as shock conditions areconcerned, there remains the possibility of premature electrical firingof the gun prior to lowering into the well, when the electrical cable orapparatus is connected to the gun. For example, stray currents orpotentials, induced by other apparatus, or accidental connection of alive electrical circuit to the gun or cable, may initiate deflagrationof the bursting charge inthe chamber and shearing and ring of thepelletl prior to the time the perforator is ready to be lowered intothecasing. As is evident, premature detonation of the-seriesv offshaped-charges while the perforator is outside the well would almostinevitably result in severe injury to nearby personnel and/or apparatus.The present invention` provides means which permits the mentionedremaining hazard to be eliminated by (a) positioning the detonable fuseout4 of the path of the pellet or particle, so that even if the pelletis tired or shot it will not, by itself, detonate the fuse, and by (b)positioning a readily inserted and readily removable detonable auxiliarycharge means in the path of the pellet and in proximity to the fuse, butsubsequent to connection of the electrical apparatus and positioning` ofthe perforator above the well and otherwise ready for lowering into thecasing. The auxiliary charge, as Well as the detonable fuse and anybooster charge thereon, are of shock-insensitive types, by which isAherein meant of types insensitive to ordinary mechanical and heat shock.encountered in normal handling operations inf the field.

In view of the foregoing, it is a primary object of the presentinvention to provide a detonator system whose employment eliminates theaforementioned remaining danger of premature initiation of firing of theshaped charges in a perforating gun.

Another object of the invention is to provide a safe detonator systemfor use in shaped-charge perforating guns.

An additional object of the invention is the provision of a casingperforator apparatus comprising only materials insensitive to ordinaryhandling shock and which will not be capable of premature detonation.

A- further object of the invention is the provision of safety means fora shaped-charge casing-perforating gun.

Other objects and advantages of the present invention will become or bemade evident upon consideration of the hereinafter described preferredphysical embodiment of apparatus illustrating the principles of theinvention, taken in conjunction with the accompanying drawings, inwhich:

Figure 1 is a view in elevation of a casing perforator incorporating theprinciples or improvements of the present invention, with sectionsremoved to improve the scale -of the drawings;

Figure` 2 is a sectional View in elevation of part of the structuredepicted in Figure 1, showing the disposition of apparatus in a sectionof a perforator, with parts broken' away;

Figure 3 is a detail view, partly in section, of a plug member employedin closing ports in a perforator'body;

only one such section may be employed, or two or more, l

as conditions and requirements of the vperforating operation dictate.Each of sections 12V above` the lowermost thereof isv provided with asubstitute joint or sub 14 at its lower end, vthe bull plug 13 servingin lieu of a sub for the lowermost of the sections. The upper part of ybody section 11 is provided with an upstanding cable 16 which comprisesone or more insulated electrical conductors 17 whose purpose is tosupply the suspended apparatus electrical current in a conventionalmanner.

Each perforator section 12v is provided with a plurality of ltapped andcounterbored apertures 18' (see Figure 2) each ofy which is providedwith a gasketed aperture-closing and element-supporting plug 19 readilyremovable therefrom by conventional driver means. The apertures 18 maybe distributed around the periphery and along the length of theperforator sections in any desired pattern or patterns. Each plug 19 isprovided with an internal tapered recess 20 arranged to receive and seatalternatively the frusto-conical end of ashapedcharge aligner 21 formingpart of an explosive-containing shaped-charge unit 22, or a meanshereinafter described in detail. Diametrally opposite each aperture 18is a respective recess 23 formed in the interior wall of the perforatorbody section, the recess being adapted to alternatively receive atubular elementhereinafter described or the cylindrical base 24 of ashaped-charge unit 22. Units 22 may be of conventional commercial formand may be of the type disclosed in the application for patent toLindsay et al., Serial No. 106,567 tiled July 25, 1949, now U.S. PatentNo. 2,707,917, issued May A length of relatively safe andshock-insensitive detonable fuse 25 (such as, for example, Primacord 50grain PETN, manufactured by Ensign-Bickford Company) is arranged in eachperforator section 12 for detonating the shaped-charge units 22 in therespective section, the fuse extending through holes formed in the bases24 of units 22, as indicated in the central section of Figure 2. One endof the detonable fusey 25 (or an auxiliary ycharge secured thereon) isfitted in a transverse aperture formed adjacent one end of a frangibletube 28 mounted transversely in the perforator section. Tube 28 ismounted in one of the endmost recesses 23 where it is secured by arespective plug 19 in a manner evident from consideration of the upperportion of Figure 2. The secured end of the Primacord 25 or, preferablyand as shown, a detonable but handling-shock insensitive auxiliarycharge 29 crimped to the end of the detonable fuse, is secured in thetransverse aperture of tube 28 by suitable means such as an elastic bandor grommet 30 secured in the aperture as indicated'in Figures 2 and 4.Tube 28, which may be formed of phenolic resin or other frangiblematerial, is preferably so formed and dimensioned as to t securely inrecess 23 and be tightly engaged by the tapered interior surface 20 ofthe associated plug 19. Auxiliary charge 29 may be in the form of a duPont P-3 metal-enclosed compressed charge of RDX type explosive of abouteleven grains weight and is preferaoly, but not necessarily, employed toinsure detonation of detonable fuse 25 in a manner hereinafter morefully explained. Mounted in the upper end of a section 12 of theperforator and in substantially axial' alignment 4 therewith, is adetonator device 32 seated and held in the perforator in a manner andmode indicated in the upper portion of Figure 2. 'Detonator device 32,which may be like or similar to thecorresponding device in theaforementioned application of Houck et al., comprises 'a main chamberedcylinder 33 having a threaded bore into which is turned a barrel orguide member 34 adapted to be firmly seated against the inner end wallof the threaded portion of the bore. Mounted in successive reduceddiameter bores formed in cylinder `33 are a shaped shear disc 35, afiber cylinder or aligner 36, and an electrically fired deflagrablecharge 37 mounted on an electrically operated igniter 38. The ignitercomprises an insulated terminal pin 39 which extends through but out ofcontact with the upper portion of cylinder 33. The detonator componentsare so made and arranged that upon application of a suitable electricpotential to pin 39 the charge contained within cylinder 36 isdefiagrated and produces su'icient pressure to cause a slug or fragmentto be sheared or broken from disc 35 and propelled along the restrictedpath provided in part by barrel 34, at high velocity. YIn the structuredisclosed in the mentioned Houck and Bradshaw application, one end of adetonable fuse, or an auxiliary charge secured thereto, was positionedin the path of the fragment, to be detonated by the latter upon firingof the defiagrable charge. It is evident that if a potential isinadvertently or accidentally applied to the igniter pin prior tolowering of the gun into a well, serious damage and injury could becaused, since in that event the perforating units would be fired withoutprotection for personnel and property.

In accordance with the present invention a detonable fuse means in theform, for example, of a length of Primacord or similar shock-insensitivefuse. with or without an auxiliary or booster charge, is positioned outof the path of the fragment. whereby premature ignition of thedeflagrable charge will not, in the absence of other means hereinafterdescribed, result in detonation of the fuse means. Rather, prematuretiring of the combustible charge 37 will only result in disruption ofthe shear disc and harmless firing of a fragment along a path in theinterior of the perforator body. According to the principles of theinvention. a readily inserted second auxiliary detonable charge isplaced in the path of the fragment, but only after all electricalconnections have been made and the perforating gun is otherwise ready tobe lowered into the well. This second auxiliary charge is insensitive toordinary shocks and is so positioned as to be in the path of thefragment, to be detonated thereby; and is also positioned in contact orclose proximity with the detonable fuse means. Thus, when inserted inthe perforator just prior to lowering of the latter into the well, thesecond auxiliary charge is adapted, when detonated by the firedfragment, to detonate the fuse means due to its close proximity to thelatter means. Prior to this arming of the perforator by insertion of thesecond auxiliary charge, the entire device and all its components arequite safe against all handling hazards in so far as personnel andnearby apparatus are concerned.

In accordance with the considerations hereinbefore expressed, a secondauxiliary charge 40 is adapted to be inserted in tube 28 and held inproper position therein by means of a compression spring 41, just priorto the perforator being lowered into the casing. Thus the perforator,including all of the explosive elements with the exception of auxiliarycharge 40, may be suspended ready for lowering into the casing, and theelectrical connections made, without danger of the shaped-charges or thedetonable fuse being accidentally prematurely exploded. Immediatelyprior to lowering of the perforator into the casing the appropriate plug19 is removed from the perforator body, an auxiliary charge 40 and itscornpression spring 41 inserted in the tube 28, and plug 19 replaced, toeffectively arm the perforator before nal lowering operations areeffected. Thereafter, passage of an electric current into terminal pin'39 in the manner explained inthe aforementioned Houck andBr'adshawapplication initiates deagr'ation of charge 37 which in turn shears apellet or fragment from shear disc 35 and propels it into detonatingimpingement with the secondary auxiliary charge 40, detonating thelatter, and initiating detonation of the detonable fuse means which inthis case includes primary auxiliary charge 29. The latter is electiveto detonate the detonable fuse 25 with great degree of certainty andthus initiate firing of the shapedcharges through which fuse 25 istrained. The auxiliary charge 40 may, for example, be a duPont type P-lOauxiliary charge comprising, for example, approximately 45-49 grains ofRDX explosive in a metal container. The two auxiliary charges 29 and 40,being insensitive to handling shock, permit complete safety to beattained with the operation of the perforator. Also, eld reloading orservicing of a perforator may be carried on by relatively unskilledlabor without danger to personnel or apparatus in the vicinity of thecasing. Further, loaded but unarmed perforators may be transportedwithout exercise of the degree of caution heretofore necessary.

In this specication and the appended claims, the terms shock-insensitiveand the like are employed as meaning insensitive to ordinary thermal andmechanical shock to which well casing perforating guns and componentsmay be subjected during normal handling procedures and including shockof such degree as would be suicient to explode ordinary blasting capsand like shock-sensitive explosive devices, but excluding shock of thedegree or intensity necessary to detonate, for example, RDX explosive.By the term initiate is meant the igniting of a deagrable charge, theexploding of an explosive charge, or the detonation of a detonablecharge, as the case may be.

As may be evident from consideration of the aforementioned copendingapplication of Houck and Bradshaw, and as is known in the art, it isimmaterial in so far as the principles of the present invention areconcerned, whether the detonator device 32 be arranged in the perforatorsection so as to fire from the bottom, or from the top, of the section.In case a plurality of perforator sections are employed, one or moreelectric ignition wires 17 may be coursed through suitable aperturesformed through the detonator devices as indicated in the upper portionof Figure 2, or in the manner and by means as disclosed in the Houck etal. application mentioned, whereby each perforator section and eachdetonator device may be supplied with ignition energy.

Further, it will be evident from consideration of the precedingdisclosure that modifications in form and structure of the disclosedpreferred embodiment of apparatus according to the invention will occurto those skilled in the art; and accordingly it is not desired to belimited to the exact details of the disclosed embodiment of apparatus,but what is claimed is:

1. A well casing perforator comprising in combination: a perforatorbody; casing-perforating units in said body; a detonator devicepositioned in said body, constructed and arranged to propel a projectilealong a given path in said body; shock-insensitive detonable fuse meanspositioned in said body out of said path and arranged to initiate saidcasing-perlorating units; arming means for said fuse means including ashock-insensitive auxiliary charge detonable by impact of saidprojectile and capable upon detonation of detonating said fuse means;means providing a path for the translation of said auxiliary charge froma rst position outside the path of said projectile to a second positionin the path of said projectile with a portion of said auxiliary chargein detonating proximity to said fuse means; and means retaining saidauxiliary charge in said second position.

2. A Well casing perforator comprising in combination: means includingcasing-perforating units arranged to be initiated by detonation of adetonable fuse means; a detonable fuse means; means including aprojectile and a projectile propellant charge and an igniter' for saidcharge; means to guide said projectile along a restrictedpath; meanspositioning said detonable fuse means out of said path; means includinga shock-insensitive auxiliary charge detonable by impact of saidprojectile and capable upon detonation of detonating said fuse means;means providing a path for the translation of said auxiliary charge froma first position outside the path of said projectile to a secondposition in the path of said projectile with a portion of said auxiliarycharge in detonating proximity to said fuse means; and means retainingsaid auxiliary charge in said second position.

3. A well casing perforator comprising in combination: a perforatorbody; a detonator device positioned in said body and including ashock-insensitlve deagrating charge and an igniter therefor, aprojectile to be propelled by said deflagrating charge, and means toguide the projectile along a restricted path; a shock-insensitivedetonable fuse means and means for positioning said detonable fuse meansout of said path; arming means for said fuse means including ashock-insensitive auxiliary charge detonable by impact of saidprojectile and capable upon detonation of detonating said fuse means;means providing a path for the translation of said auxiliary charge froma irst position outside the path of said pro- I and a plurality ofexplosive casing perforating units therein arranged to be initiated bydetonation of a detonable fuse means, in combination with said body andunits: a detonable fuse means in said body arranged to detonate saidperforating units and positioned out of a restricted path therein; aprojectile and means in -the body to propel the projectile along saidpath at-high speed; auxiliary detonable means positioned in said tubularbody with a portion thereof in said restricted path and adapted to bedetonated by said projectile and another portion thereof in closeproximity to said fuse means and adapted to detonate the latter; supportmeans in said tubular body supporting said auxiliary detona-ble means;and means including aperture means in the wall of said tubular bodythrough which said auxiliary detonable means is inserted into saidtubular body and into said support means.

5. A well casing perforator comprising, in combination: a tubularperforator body section having a plurality of lateral apertures thereinand internal recesses each diametrally opposite a respective lateralaperture; a plurality of shock-insensitive detonable shaped-chargeperforating units, each disposed at a respective one of said recesses; aplurality of plugs, one for each of said apertures; shock-insensitivedetonable fuse means arranged to detonate said perforating units uponbeing detonated; supporting means extending transversely of said bodysection and mounted in one of said apertures and its respective recess,and arranged to support an end of said fuse means in a predeterminedlocation; shock-insensitive means in said body section including aprojectile and means for firing the projectile along a path outside saidlocation and intersecting said supporting means; and shock-insensitivedetonable auxiliary charge means, insertable through the aperture inwhich said supporting means is mounted, disposed in said supportingmeans in said path and in detonating proximity to said end of said fusemeans, whereby detonation of said fuse means and said perforating unitsmay be initiated only by insertion of said auxiliary charge means insaid supporting means prior to tiring of said projectile along Saidpath.

(References on following page) UNITED STATES PATENTS 1,322,083 BarlowNOV. 18, 1919 2,265,982 Bolton Dec. 16, 1941 2,452,072 Schatz Oct. 26,1948 55 Muskat et al. Jan. 10, 1950 Martin NOV. 21, 1950 Morris Nov. 11,1952 Sweetman Feb. 24, 1953 Turechk et al. Dec. 15, 1953

